4 wheel drive question

[gerard]

Do a search on how a differential works. There are some pretty good explanations that show how a differential works. (There s areally good one that's about 50 years old that uses a spoked wheel to illustrate it, think it was by gm). Once you see how a differential works it becomes pretty clear.

 

[LD1]

I believe that they currently use electronic lockers (eLocker) that are only activated in Low range along with a part-time transfer case.

Thats kinda what I was thinking it could be, but if I owned one, I'd be figuring out how to control the lockers seperatly.

There are a lot of times lockers would be nice in 4H as well.

Or even 2H if you wanted to lay a nice patch of rubber out front. It would be nice to activate JUST the rear one.:thumbsup:

 

[Mace Canute]

In another thread (can't find it now), a gentleman said that he hadn't seen any differentials in any of the tractor front axles he had worked on which would make them just an angle drive. It would be easy enough to check on your own individual tractors.

 

[Heywood Jannockitov]

But I will add one thing. When you are stuck, whether it be tractor or truck, and you are one-wheel-peeling at the axle.....The tire that IS spinning is doing so at twice the normal rate.

I actually observed this first-hand last week when I had our Mule 610 jacked-up with the rear wheels off to check the brakes. My MIL thought they were dragging (they weren't). After reading about this "phenomenon" in another thread, I decided to do an experiment.

With the motor running slightly above idle, in gear and in 2wd with the rear tires off, I observed both drums turning forward slowly. I grabbed the brake drum on one side and held it motionless.

Sure enough, the drum on the other side sped up twice as fast. :thumbsup:

 

[pat32rf]

For those times when you are "hi-centered" with open differentials, sometimes gently applying the brakes will stop the airbourne wheel from spinning enough to transfer torque to the traction wheels.
A "locking" front dif could be a problem in a tractor because of the short wheelbase and sharper turns than you get in a truck or car. A "viscous" locker should work in the front but again even it could be troublesome in the rear on sharp turns....
Sounds like full time fwd (with aux locks) is the answer instead of the part time systems used in CUTs now

 

[LD1]

For those times when you are "hi-centered" with open differentials, sometimes gently applying the brakes will stop the airbourne wheel from spinning enough to transfer torque to the traction wheels.

That was common practice before rear diff locks became almost standard.

 

[k0ua]

For your viewing pleasure: YouTube - How Differential Gear works (BEST Tutorial)

This is the 1930's video. a little dated, but I think it is the best tutorial I have seen to explain the operation.

 

[SixHoeBob]

Can someone explain how differential steering works on a D8N Caterpillar?

I know, but it is too much bother to explain. Does anyone even care?

Just another example of a use for a differential.

 

[Raspy]

Four wheel drive systems in trucks (no transfer case differential and open axle differentials) are not two wheel drive! And two wheel drive trucks are not "one" wheel drive.

An open differential (no locker and no limited slip) ALWAYS applies equal torque to both wheels. If you get stuck and observe one front and one rear wheel spinning, it's because those two spinning wheels have the least traction, but both wheels on each axle are receiving the same torque. The wheels that are not spinning are applying the exact same torque to the ground.

An open differential means equal torque to both wheels, but unequal speed. A locked differential means always equal speed, but unequal torque. This is basic differential theory.

When someone applies the brake to help with a spinning tire on an open differential, they are adding friction, not only to the two rear wheels equally, but also to the front wheels. If anything, this will make it harder to move. Dune buggies often have a lever to apply the brakes to individual wheels. In this case you can add braking to the spinning wheel. This will add torque to the non-spinning wheel and help you move.

This idea that trucks are one wheel drive is an old myth that just won't die.

 

[Raspy]

For your viewing pleasure: YouTube - How Differential Gear works (BEST Tutorial)

This is the 1930's video. a little dated, but I think it is the best tutorial I have seen to explain the operation.

That's a great video. After all these years there is still so much misunderstanding of the simple differential. I can't count how many times I've heard the "one wheel drive" tale.